Transmitting apparatus for railway train communicating systems



2 Sheets-Sheet 1 SS SQ S QREQ QQN Q P. N. BCIJSSART Filed March 20, 1942 Feb. 2, 1943.

TRANSMITTING APPARATUS FOR RAILWAY TRAIN COMMUNICATING SYSTEMS Feb. 2, 1943. bss 2,309,747 JTRAN'SMITTING APPARATUS FOR RAILWALTRAIN COMMUNICATING SYSTEMS I 2 Shefcs-Sheet 2 I Filed March 20, 1942 1 [hm/V7011.-

m Y .ww RQ QQBQ v r Patented Feb. 2, 1943 UNHTED STATES PATENT OFFICE TRANSMITTING APPARATUS FOR RAILWAY TRAIN COMMUNICATING SYSTEMS Paul N. Bossart, Cheswick, Pa., assignorto-The Union Switch & Signal Company, SWissval Pa., a corporation of Pennsylvania Application March 20, 1942, Serial No. 435,440

11 Claims. (Cl. 246 -8) My invention relates to transmitting apparatus for railway train communication systems, and more particularly to transmitting apparatus for communication systems for railway yards.

A railway yard is sometimes equipped with a public address system having loud speakers at various points about the yard whereby the yard ofiice can communicate with conductors and other switching crew members when in the vicinity of one of the loud speakers. Also, railway yards are sometimes equipped with communication systems capable of transmitting direct from the yard ofiice to loud speakers or cab signals in the cabs of switching locomotives operating in the yard.

A feature of my invention is the provision of novel and improved apparatus that may be readily conditioned to transmit a voice frequency telephone current to loud speakers placed at various locations in the railway yard, or a carrier telephone current to receiving apparatus on a vehicle of a train operating in such yard, or to provide both such services simultaneously.

Other features, objects and advantages of my invention will appear as the specification progresses.

The above features, objects and advantages of my invention are accomplished by providing novel switching means for transmitting apparatus that can be conditioned to supply either a carrier telephone current or a, voice frequency telephone current to a transmitting circuit extending along a railway track. At one position of the switching means the transmitting apparatus is conditioned to supply a carrier telephone current to actuate a train carried telephone receiver or other cab signal when the train is operating on such railway track. At a second position of the switching means, the transmitting apparatus is conditioned to avoid modulation of the carrier by the voice frequencies and to bypass the usual band pass filter, and a voice frequency telephone current is supplied to actuate loud speakers coupled to the transmitting circuit through low pass filters which pass voice frequencies but substantially block the carrier frequency. Both such purposes are accomplished simultaneously by providing the transmitting apparatus with a carrier frequency channel and a voice frequency channel and by arranging the switching means with a third position in which both channels are made active simultaneously.

I shall describe two forms of apparatus -em bodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a diagrammatic 'view showing one form of apparatus embodying my invention for transmitting either a voice frequency telephone current or a carrier telephonecurrent but not both simultaneously. Fig. 2 is a diagrammatic viewshowing another formof apparatus embodying my invention for transmitting either 'a, voice frequency current or a carrier telephone current, or both simultaneously. In each of the two views, like reference characters are used to designate similar parts.

It is to be understood that my invention is not limited in its use to railway yards, but it has peculiar advantages when so used.

Referring to Fig. 1 a single line diagram at the lower portion of the drawing illustrates the tracks of a railway yard indicated as a whole by the reference character CY, it being understood that the yard CY is not limited to three tracks as shown in the drawings. These tracks may be arranged for hump switching or for flat switching. The track rails of each track may be bonded in the usual manner to improve their electrical conductivity, but such bonding may not be required since the rails are electrically continuous due to the splice bars and bolts of the rail joints. I V

A line wire Ll extends between designated limits of the yard CY, and maybe an open wire strung on a pole line through or along one side'of the yard, or it may be a conductor carried in a' conduit. The conduit should be preferably nonmetallic, or of metallic, ungrounded. The line wire LI and the track rails of the different tracks in multiple are included in a transmitting circuit to be more fully explained hereinafter.

Two loud speakers LSI and LS2 are located at suitable points in the yard CY, but it will be understood that additional loud speakers may be provided as required. Each loud speaker LS is connected to the transmitting circuit through a low pass filter LPF having one terminal connected to line wire LI and the other terminal connected to a ground electrode which may be the rails of a track in the vicinity of the speaker. Each such low pass filter LPF is proportioned to pass voice frequencies of a predetermined range such as from 40.0 to 3000 cycles per second. That is to say, each low pass filter LPF has an upper cuteoff frequency of about 3000 cycles per second.

The reference character YO designates a yard ofiice from which switching and other Work about the yard are directed by means of a communication system using the transmitting circuit ineluding line wire Ll, the transmitting apparatus of the system being located at the yard ofiice YO. At the point most remote from the office YO, the line wire Ll is connected to ground or to the rails of a railway track through a condenser C l Which condenser is proportioned to readily pass frequencies above the predetermined range of voice frequencies and to block currents in the voice frequency range.

The transmitting apparatus at the yard oifice YO is indicated as a whole by the reference character TA and its construction may take any one of several forms. As shown in Fig. 1, the construction of the transmitting apparatus TA is similar to that disclosed in Letters Patent of the United States No. 2,129,313, granted September 6, 1938, to L. D. Whitelock for Apparatus for electric signaling systems. It is sufiicient for the present disclosure to point out that such transmitting apparatus comprises a microphone M, a carrier current generator or oscillator OSL, a balanced electron tube modulator MO, a band pass filter BPF and a power amplifier PA. Microphone M is provided with a circuit including a suitable source of direct current, the terminals of which are indicated by B and C, and a winding 56 of a transformer Tl which is coupled to the grids 1 and 8 of electron tubes 4 and 5, respectively, of modulator- MO, the connections to the grids of these tubes being such that the voice frequencies created in the transformer Tl due to speaking into the microphone M are impressed on the grids of the tubes 180 degrees out of phase.

The carrier current generator or oscillator OSL is shown conventionally, since its specific structure is immaterial and it may be of any one of several forms, such as the electron tube oscillator. The output side of oscillator OSL is connected across a resistor l3 interposed in the cathode side of the grid circuits oftubes 4 and 5, so that the carrier current supplied by oscillator OSL is impressed on the modulator tubes 4 and '5 in phase to be modulated by the voice frequencies created at the microphone M. The plate circuits for tubes 4 and 5 include a source of direct current whose terminals are indicated at B300 and N300, together with windings 22 and 23 of a transformer T2, the winding 22 and 23 being of the well-known push-pull arrangement whereby the carrier is balanced out and the side bands resulting from modulation of the carrier by the voice frequencies appear in the output winding 36 of transformer T2. Winding 36 of transformer T2 is made a part of band pass filter BPF proportioned to ass a preselected one of the side bands only. As an aid in the understanding of the apparatus, I shall assume by way of example that the oscillator OSL delivers a carrier current of a frequency of 5700 cycles per secend, the voice frequency range for modulation purposes extends from 400 to 2500 cycles, and the filter BPF selects the upper side band. Hence there appears at transformer T3 at the output side of filter BPF a single side band carrier telephone current having a frequency range of 6100 to 8200 cycles.

Power amplifier PA consists of two electron tubes 6 and 1 having their grid circuits connected to windings 24 and 25, respectively, of transformer T3, and their plate circuits connected to windings 26 and 21, respectively, of an output transformer T4 in parallel arrangement, with the result that the single side band telephone current passed by filter BPF is amplified and inductively at a relatively high energy level. Winding 28 is connected to the transmitting circuit by having one terminal connected to line Wire LI and the other terminal connected to ground electrode 29. This ground electrode may be, if desired, the rails of one or more of the tracks in the vicinity of the yard ofiice.

According to my invention, I provide the transmitting apparatus TA with switching means which in Fig. 1 includes a. manually operable circuit controller in the form of a push button-PBI provided with three contact members 30, 3| and 32. Push button FBI is preferably of the spring return type biased to a number one position wherein the three contact members ocfcupy the positions illustrated by solid lines in the drawings, and depressible to a number two position wherein the contact members are moved to the positions illustrated by dotted lines in the drawings. Contact member 30 when moved to the number two position completes a connection between one terminal of oscillator. OSL and a ground electrode 34 to shunt the oscillator away from modulator MO and so to avoid modulation of the carrier by the voice frequencies. Contact member 3| at the number two position connects winding 23 of transformer T2 through a condenser 35' to a preselected mid terminal of winding 25 of transformer T3. Similarly, contact member 32 at the number two position connects winding 22 of transformer T2 through a contransferred to a winding 28 of transformer T4 denser 36 to a preselected mid terminal of winding 24 of transformer T3. In other words, contacts 3| and 32 serve to complete circuit connections by which the plate circuits of tubes 4 and 5 of modulator MO are coupled to the grid circuits of tubes 6 and 1 of power amplifier PA around the band pass filter BPF. Condensers 35 and 36 serve to block the direct voltage from the B300--N300 source of the plate circuits of tubes 4 and 5 from the grid circuits of tubes 6 and I of the power amplifier. It follows that when push button PBI occupies its number one position, the transmitting apparatus TA is conditioned to supply an upper side band carrier telephone current having a frequency range of 6100 to 8200 cycles, and this carrier telephone current flows in the line wire LI and in the rails of each track of the yard CY, but is ineffective to actuate ,the loud speakers LSI and LS2 due to the low pass filters LPF by which the loud speakers are connected to the transmitting circuit. When push button FBI is depressed it shunts the carrier current from the modulator to avoid mixing with the voice frequencies, the tubes 4 and 5 function as amplifiers, and the plate circuits of the tubes 4 and 5 are coupled to the grid circuits of tubes 6 and 1 of the power amplifier by connections which by-pass the filter BPF, with the result that a voice frequency telephone current of relatively high energy level is supplied to the transmitting circuit. This voice frequency telephone current is passed by each low pass filter LPF to the associated loud speaker.

A locomotive indicated conventionally at L0 is provided with receiving apparatus including a receiving coil RC mounted on the locomotive in inductive relation to the rails and connected to a telephone receiver or loud speaker LS3 through a demodulator shown conventionally at DO. Such train carried receiving apparatus may be of any suitable type, such, for example, as that disclosed in Letters Patent of the United States No. 2,064,639, granted December 15, 1936, to L. D. Whitelock et al., for Communicating System.

Thus the carrier telephone current supplied to the transmitting circuit by the apparatus at the yard office YO in the manner explained hereinbefore, is received by the apparatus on locomotive L and the voice frequencies are reproduced at the loud speaker LS3. I

It is to be seen therefore that in Fig. 1 communication can be effected between the yard office Y0 and locomotive LO when it is at any point about the yard CY by conditioning the transmitting apparatus TA to supply a carrier telephone current, and communication between the yard ofiice Y0 and the loud speakers LS! and LS2 can be effected by depressing the push button PB! to condition the transmitting apparatus to supply a voice frequency telephone current.

In Fig. 2, a railway yard CY is provided with a transmitting circuit including line wire Ll, loud speakers LSI and LS2 are connected to the transmitting circuit through low pass filters LPF, operation of the yard is directed from a yard ofiice Y0, and a locomotive L0 is equipped with carrier telephone current receiving apparatus, all as in Fig. 1. The transmitting apparatus at yard ofiice YO of Fig. 2 is indicated as a whole by reference character TAI, and this transmitting apparatus includes a microphone M, a carrier current generator OSL, an electron tube modulator MO, a band pass filter BPF, and a power amplifier PA, all as in Fig. 1. The manually controlled push button FBI and the circuit connections associated therewith of Fig. 1, are, in Fig. 2, replaced by a three-position manually operable circuit controller CC, an electron tube amplifier 50 and a transformer T5, together with a special winding 5| on transformer T3. Apparatus TAI includes a carrier frequency channel comprising transformer Tl, modulator MO, oscillator OSL and band pass filter BPF, by means of which a carrier telephone current is applied to power amplifier PA and in turn to the transmitting circuit. Apparatus TAI includes also a voice frequency channel comprising transformer T5, amplifier tube 50 and winding 5|, by means of which a voice frequency telephon current is applied to power amplifier PA and in turn to the transmitting circuit. Circuit controller CC is manually operable to move its three circuit contact members 52, 53 and 54 in unison to any one of three positions indicated by the numerals I, 2 and 3.

Circuit controller CC selectively controls the two channels of the transmitting apparatus TAl by governing the connections of, the microphone M to the different channels. At the number one position of circuit controller CC, a microphone circuit can be traced from terminal B over microphone M. contact member 53 of controller CC in number one position, resistor 55, winding 56 of transformer TI, and inductor 51 to terminal C. Thus voice frequencies produced in microphone M are transferred through transformer-Ti to modulator MO and a carrier telephone current is supplied to the transmitting circuit in the main ner explained hereinbefore. The plate circuit of tube 50 is open when contact 52 of circuit controller CC is in its number one position, but is closed when this contact is in either its number two or its number three position. At the number three position of controller CC, a microphone circuit can be traced from terminal B over microphone M, Winding 58 of transformer T5, resistor 55, contact member 54 of controller CC in its number three position, and inductor 5'! to terminal C. Thus, at the number three position the voice frequencies produced in microphone M are applied to the rid circuit of tube 50 through transformer T5, and such voicefrequencies are amplified in the platecircuit of tube 58, which plate. circuit includes winding 5! of transformer T3; with the result that the voice frequency current is applied to the power amplifier PA and in turn to. the transmitting circuit. At the number two position of controller CC a microphone circuit can be traced from terminal B through microphone M, winding 55 of transformer T5, number two position of contact members 53 and 54 of controller CC, winding 55 of transformer Ti and inductor 57 to terminal C; Hence the voice frequencies produced in microphone M- are now applied to both channels with the result that a carrier telephone current and a voice frequency telephone current are simultaneously supplied to the transmitting circuit. The carrier telephone current supplied to the transmitting circuit of Fig. 2, is received by the apparatus of locomotive L0, and the voice frequency telephone current is received by each loud speaker LS5 and LS2, all as explained in discussing Fig. 1.

It will be seen, therefore, that with the apparatus shown in Fig. 2, communication can be accomplished either between the yard ofilce Y0 and locomotive L0, or between the yard ofiice and the trackside loud speakers, and that both such services can be effected simultaneously.

Apparatus embodying my invention has the advantages that the yard master can communi-' cate with the conductors of yard crews who are usually on the ground, or he can communicate with the locomotive crew, or he can coznmunicate with both simultaneously.

Although I have herein shown and described but two forms of transmitting apparatus for railway train communication systems embodying my invention, it is understood that various changes and modifications may be made therein within the scope ofthe appended claims without de parting from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In communication apparatus for use with a transmitting circuit including the rails of a railway track and a line wire extending along such track, the combination comprising; wayside station means including a microphone, a carrier frequency generator and a modulator coupled to sa d transmitting circuit to supply thereto a carrier telephone current; and wayside station switching means operative to condition said first mentioned wayside station means to. supply to the transmitting circuit a voice frequency telephone current.

2. In communication apparatus for use with a transmitting circuit including the. rails of a railway track and a line wire extending along said track, the combination comprising; wayside station means including a microphone, a carrier frequency generator and a modulator coupled to said transmitting circuit to supply thereto a carrier telephone current; other wayside station means including said microphone. and an amplifying means coupled to said transmitting circuit to supply thereto a voicefrequency telephone current. and switching means to selectively govern said two Wayside station means.

3. In communication apparatus for use with a transmitting circuit including the rails of a railway track and a line wire extending along such track, the combination comprising, carrier telephone current receiving means mounted on a train ,that travels said track and coupled to said transmitting circuit, a loud speaker located in the trackway and connected to said transmitting circuit through a low pass filter, a microphone located at a Wayside station along said ,track, a first transmitting means at said wayside station to couple said microphone to said transmitting circuit and including a carrier current generator and a modulator to supply a carrier telephone current for communication with said train, a second transmitting means at said wayside station to couple said microphone to the transmitting circuit and including an amplifier to supply a voice frequency telephone current for communication with said loud speaker, and switching means to selectively control said first and second transmitting means.

4. In communication apparatus for use on a railway along a track of which extends a transmitting circuit including a line wire, the combination comprising, carrier telephone current receiving means mounted on a train which travels said track and coupled to said transmitting circuit, a voice frequency telephone current receiver located in the trackway and connected to said transmitting circuit through a low pass filter; transmitting apparatus at a station along said railway and including a microphone, a carrier current generator, a modulator and an amplifier and having a first and a second condition for supplying either a carrier telephone current or a voice frequency telephone current; means to couple said transmitting apparatus to said transmitting circuit, and switching means including a multiple position circuit controller to selectively control the conditions of said transmitting apparatus.

5. In communication apparatus for use at a railway yard in which a locomotive provided with carrier telephone current receiving means coupled to the rails operates and which yard is equipped with trackway loud speakers, the combination comprising, a transmitting-circuit including the rails of the tracks of said yard and a line wire extending along the yard, low pass filters for connecting said loud speakers to said line wire, a yard oifice; transmitting apparatus including a microphone, a carrier frequency generator and a modulator located at said yard oflice and coupled to said transmitting circuit to supply thereto a carrier telephone current for communication from the yard office to said locomotive, and means including a manually operable circuit controller to condition said transmitting apparatus to supply to said transmitting circuit a voice frequency telephone current for communication between the yard office and each of said loud speakers.

6. In communication apparatus for use at a railway yard in which there operates a locomotive having mounted thereon carrier telephone current receiving apparatus in inductive relation to the rails and which yard is provided with trackway loud speakers, the combination comprising, a transmitting circuit including the rails of the tracks of said yard and a line wire extending along the yard, low pass filters of a predetermined upper cut-off frequency for connecting said loud speakers to said line wire, a yard ofice; transmitting apparatus including a microphone, a generator of a carrier current of a predetermined frequency and a modulator located at said omce and coupled to said transmitting circuit to supply a carrier telephone current thereto for communication with said locomotive, and yard ofiice switching means to condition said transmitting apparatus to supply to the transmitting circuit a voice frequency telephone current for actuating each of said loud speakers.

7. In communication apparatus for use at a railway yard in which there operates a locomotive provided with carrier telephone current receiving apparatus coupled to the rails and which yard is provided with trackway loud speakers. the combination comprising, a transmitting circuit including the rails of the tracks of said yard and a line wire extending through the yard, low pass filters for connecting said loud speakers to said line wire, a yard ofilce; transmitting apparatus including a microphone, a carrier frequency generator, an electron tube modulator and a band pass filter at said oilice and coupled to said transmitting circuit to supply thereto a carrier telephone current for communication with said 10- comotive; and manually operable yard ofiice switching means operative to shunt said generator and to by-pass said band pass filter for conditioning said transmitting apparatus to supply voice frequency telephone current to said transmitting circuit for communication with said loud speakers.

8. In combination, a microphone, a carrier frequency current generator, a modulator including two electron tubes having grid circuits coupled to said microphone and to said generator to modulate said carrier current by voice frequencies, said tubes being provided with pushpull plate circuits, a band pass filter coupled to said plate circuits to pass a preselected side band resulting from said modulation, a transmitting circuit coupled to said filter to be supplied with such single side band carrier current, and circuit means including a manually operable circuit controller to shunt said generator and to by-pass said filter to permit voice frequency telephone current to be supplied to said transmitting circuit.

9. In combination, a microphone, a carrier frequency generator, a modulator including an lectron tube having a grid circuit coupled to both said microphone and said generator to modulate said carrier current by voice frequencies, means including a band pass filter connected to the plate circuit of said tube to suppress said carrier frequency and pass a preselected side band of the modulation to a transmitting circuit to supply the transmitting circuit with a single side band carrier telephone current; and circuit means including a circuit controller having contacts operative to divert said carrier current away from said modulator tube, and to by-pass at least a portion of said filter to supply to said transmit ting circuit a voice frequency telephon current.

10. In communication apparatus for use with a railway track over which there operates a locomotive provided with carrier telephone current receiving apparatus coupled to the rails and along which track there is provided a loud speaker, the combination comprising, a transmitting circuit including the rails of said track and a line wire extending along said track, a low pass filter to connect said loud speaker to said transmitting circuit, wayside station transmitting apparatus including a microphone and two channels to couple the microphone to said transmitting circuit; one of said channels including a generator of a carrier current of a predetermined frequency, a modulator and a band pass filter to supply a side band carrier telephone current circuit to supply thereto a carrier telephone current; a second telephone channelincluding an electron tube amplifier to couple said microphone to said transmitting circuitfto supply thereto a voice frequency telephone current, and circuit means including a three-position circuit controller to connect said microphoneto said first channel at a first position of said controller, to said second channel at a third position of said controller and to both of said channels at a second position of said controller. 1

PAUL N. BOSSART. 

